JPH10230544A - Method for blow molding of hollow molded product and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To deform a parison without being accompanied by the local curing thereof so as to almost perfectly follow the shape of a cavity by blowing air toward the peripheral surface of the parison from the cavity surface of a mold until a mold is perfectly clamped to bring the parison and the cavity to a non- contact state. SOLUTION: Until molds 11, 12 approaching and separating each other are perfectly clamped, a changeover valve 17 is opened to blow air (hot air) toward the peripheral surface of a parison P from the vent holes 15 provided to the cavity surfaces 13, 14 of the molds 11, 12 to bring the parison P and cavities 13, 14 to a non-contact state. After the mold clamping of the molds 11, 12 is completed, the changeover valve 17 is closed corresponding to the command from an air supply and discharge control part 18 and the blowing-off of air from the vent holes 15 is stopped and the parison P is deformed so as the follow the shapes of the cavities of the molds 11, 12 to obtain a desired hollow molded product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention provides a parison between a pair of mutually separated male and female molds, closes the molds to sandwich the parison between the two molds, and then places the parison in the parison. The present invention relates to a method and an apparatus for blowing air to blow-mold a hollow molded product.

[0002]

2. Description of the Related Art Various methods and apparatuses for blow molding a hollow molded article of this kind have been developed and are disclosed in JP-B-61-32128.
And Japanese Patent Application Laid-Open No. 9-11322.

[0003]

Of the above-mentioned publications, the former is limited to the one that forms a curved tube made of a plastic material, and is not versatile. Also, before the parison is sealed in the mold, the parison is adsorbed on the cavity surface of the female mold, and the parison tends to harden locally on the suction surface, and the hardening is performed when the mold is closed and air is blown into the parison. The parison surface is subjected to a tensile force in the surface direction, and fine cracks are formed in the hardened parison surface, causing a skin roughening phenomenon.Also, due to the hardening of the parison and the roughening of the parison, the parison becomes a cavity surface shape of a mold. Without copy deformation, transferability is reduced and uneven thickness is likely to occur. In the latter publication,
A method and a mold are disclosed in which a fluid is sprayed toward a portion of a parison having a small thickness change contained in a cavity surface and fluid is removed from a portion of the parison having a large thickness change. However, in order to carry out this method, it is necessary to complicately form a partial outflow port and a discharge port and a fluid adjustment chamber connected to them in accordance with the unevenness of the cavity surface, and to provide a pipe having a fluid diameter to be supplied thereto. Although the operation and the control system become extremely complicated, the use of resin is saved. However, as the mold becomes more complicated, the cost of the mold increases, which ultimately affects the product cost. The present invention provides a blow molding method of a hollow molded article in which the structure of the cavity surface is improved, the transferability of the hollow molded article is improved, and uneven thickness is prevented from occurring, in order to improve the above-mentioned disadvantages of the prior art. The purpose is to provide the device to the market.

[0004]

In order to achieve the above-mentioned object, a specific invention is to hold a parison supplied between dies which are close to each other and blow air into the held parison to form a hollow molded article. In the method of blow molding, air is blown from the cavity surface of the mold toward the parison peripheral surface until the mold is completely clamped, so that the parison and the cavity surface are in a non-contact state. A blow molding method for a hollow molded product, wherein the blowing of the air is stopped when the mold is completely closed, and the parison is deformed in accordance with the shape of the cavity surface of the mold by blowing the air into the parison. I do.

In order to achieve the above object, the temperature of air blown from the cavity surface toward the peripheral surface of the parison in this blow molding method is set to a temperature lower by 10 to 30 ° C. than the melting temperature of the resin of the parison. It is characterized by.

In order to achieve the above object, the present invention is characterized in that male and female dies which are close to and separated from each other are used as the dies in the blow molding method, and a hollow double-walled molded product is blow-molded.

In order to achieve the above object, when the mold is completely clamped in the blow molding method, the blowing of the air is stopped, and the air remaining in the gap between the mold cavity surface and the parison is sucked. At the same time, the parison is deformed in accordance with the shape of the cavity surface of the mold by blowing air into the parison.

[0008] In order to achieve the above object, a related invention is a blow molding apparatus for a hollow molded article characterized by performing the blow molding method for a hollow molded article according to the first, second, third, or fourth aspect.

In order to achieve the above object, a large number of ventilation holes are provided on the cavity surfaces of the molds which are close to and separated from each other in the blow molding apparatus. In these ventilation holes, an air supply source is provided via a switching valve. Connected, air is supplied from the air supply source to the vent until the mold is completely clamped. When the mold is completely clamped, the switching valve is switched, and the air supply is stopped. An air supply control unit is provided.

To achieve the above object, a heater is provided on the secondary side of the air supply source in the blow molding apparatus.

In order to achieve the above object, the mold in the blow molding apparatus is characterized in that it is a mold for a hollow double-walled molded product.

In order to achieve the above object, the blow molding apparatus is provided with the heater for heating air from the air supply source to a temperature lower by 10 ° C. to 30 ° C. than a melting temperature of the parison resin. Features.

In order to achieve the above object, a pressure reducing device is connected to the vent hole of the blow molding device in parallel with an air supply source via the switching valve, and the supply of the air is stopped. An air supply / discharge control unit for activating the pressure reducing device is provided to suck air remaining in the gap between the cavity surface of the mold and the parison at the time of the operation. In this specification, the term "non-contact between the mold and the parison" means a state in which there is a slight air layer between the two and the parison is slippery with respect to the cavity surface-surface, and means only complete non-contact. is not.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical embodiment of the device invention according to the fifth, sixth, seventh, eighth, ninth and tenth aspects will be described. FIG.
In the figure, reference numeral 10 denotes a blow molding apparatus for hollow molded articles. In the blow molding apparatus 10, a large number of air holes 15 are provided in the cavity surfaces 13, 14 of the molds 11, 12 which are close to and away from each other, penetrating from the back surface of the molds 11, 12 toward the inner surface. The air supply source 1 is
6 and the pressure reducing device 20 are connected in parallel via the switching valve 17. Until the clamping of the dies 11 and 12 is completed, air is supplied from the air supply source 16 to the vent hole 15. When the clamping of the dies 11 and 12 is completed, the switching valve 17 is switched. While stopping the supply of this air,
Cavity surfaces 13 and 14 of molds 11 and 12 and parison P
In order to suck air remaining in the gap between
An air supply / discharge control unit 18 that activates 0 is provided. The dies 11, 12 are dies for hollow double-walled molded products.
A heater 1 for heating the air from the supply source 16 to a temperature lower by 10 ° C. to 30 ° C. than the melting temperature of the resin of the parison P
9 is provided on the secondary side of the air supply source 16. The molds 11 and 12 preferably hold the parison P supplied between the male and female molds 11 and 12 which are close to and separated from each other, and the parison front and back films are formed by the air pressure blown into the held parison. A pair of male and female molds 11 and 12 are formed along the inner surface of the female mold to bulge in the same direction and individualize to produce an article having inner and outer double walls. Box-shaped female mold 11
Consists of a pair of two peripheral wall members and a bottom member, and these peripheral wall members are in contact with the bottom member at a position retracted outward and close to the bottom member and other adjacent peripheral member members. It is equipped so as to be able to reciprocate linearly or oscillate between the contact and the position where the desired female mold shape is formed. The operation of the blow molding apparatus will be described as a typical embodiment of the method invention described in claims 1, 2, 3, and 4.

[0015] The parison P supplied between the dies 11 and 12 approaching and separating from each other is sandwiched, and air is blown into the sandwiched parison P to blow-mold a hollow molded product. Until the mold is completely closed, the switching valve 17 is opened, and air (warm air) is blown out from the ventilation holes 15 provided in the cavity surfaces 13 and 14 of the dies 11 and 12 toward the parison P peripheral surface. The parison P and the cavity surfaces 13 and 14 are almost in a non-contact state. When the clamping of the dies 11 and 12 is completed, the switching valve 17 is closed in response to a command from the air supply / discharge control unit 18 to stop blowing air from the ventilation holes 15, and The parison P is deformed following the shape of the cavity surfaces 13 and 14 of the molds 11 and 12 by blowing air into the
Obtain the desired hollow molded article. When the molds 11 and 12 are completely shut off, the parison P is placed on the cavity surfaces 13 and 1.
4, the parison P slides on the cavity surfaces 13, 14 with a slight air layer interposed therebetween, and a part of the parison P is hardened and the thickness of the parison P does not change. 14 follows the shape. Dies 11, 12
Until the air is completely shut off, excess air will be
It is emitted to the outside from the mating portion of 1, 12. Further, the air remaining between the cavity surfaces 13 and 14 of the molds 11 and 12 and the parison P is sucked through the air holes 15 by the operation of the pressure reducing device 20 (see FIG. 2). The temperature of the air blown out from the air holes 15 of the cavity surfaces 13 and 14 toward the peripheral surface of the parison P is set to a temperature lower by 10-30 ° C. than the melting temperature of the resin of the parison P by the heater 19. Is preferred from above. In this way, a hollow double-walled molded product without uneven wall thickness is blow-molded.

[0016]

According to the first aspect of the present invention,
In a method in which a parison supplied between molds approaching and separating from each other is sandwiched, air is blown into the sandwiched parison, and blow molding is performed on a hollow molded product, the above-described method is used until the mold is completely clamped. From the cavity surface of the mold toward the parison peripheral surface, air is blown out, the parison and the cavity surface are brought into a non-contact state, and when the mold clamping of the mold is completed,
This method is a blow molding method of a hollow molded product, in which the blowing of air is stopped, and the parison is deformed in accordance with the shape of the cavity surface of the mold by blowing air into the parison. Since the parison does not contact the cavity surface until the tightening is completed, the parison can be almost completely deformed by following the cavity surface shape without local hardening of the parison, and the transferability of the hollow molded article can be improved. In addition, the blowing and sucking of air from the cavity surface is a simple method, and the control method is also simple.

In the invention described in claim 2, in addition to the above effects, the temperature of the air blown from the cavity surface toward the peripheral surface of the parison is set to a temperature lower by 10 ° C. to 30 ° C. than the melting temperature of the resin of the parison. Since the blow molding method for blow molding a hollow molded article is characterized in that the parison is not cured by the blown air, the process can proceed to the blow molding step.

According to the third aspect of the present invention, in addition to the above effects, a hollow double-walled molded product such as a bathtub, a freezer,
Blow molding of planters, U-shaped grooves for drainage, etc. can be performed without unevenness.

According to the fourth aspect of the invention, in addition to the above-mentioned effects, the parison can be surely copied on the cavity surface to be deformed, and the transferability can be further improved.

According to the fifth aspect of the present invention, the first, second,
The method inventions described in 3 and 4 can be carried out, and the effects can be exhibited.

In the invention according to the sixth aspect, in addition to the above-mentioned effects, an air supply control unit for stopping the supply of air to the vent when the mold is completely closed is provided, so that air to the parison is provided. The blowing can be appropriately controlled according to the opening and closing of the mold, and the transferability of the hollow molded article can be improved.

According to the seventh aspect of the present invention, in addition to the above effects, the temperature of the air supplied to the ventilation hole can be set to a temperature suitable for heating the parison by the heater.

According to the eighth aspect of the present invention, the third aspect is provided.
The described method invention can be implemented, and its effects can be exhibited.

According to the ninth aspect of the present invention, the second aspect is provided.
The described method invention can be carried out and its effects can be exhibited.

According to the tenth aspect of the present invention, the method of the fourth aspect of the present invention can be implemented and its effects can be exhibited.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a state at the time of air blowing in an embodiment.

FIG. 2 is a schematic diagram showing a state at the time of completion of mold clamping of the mold of FIG. 1;

[Explanation of symbols]

 P Parison 10 Blow molding device 11, 12 Mold 13, 14 Cavity surface 15 Vent

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B29L 24:00

Claims (10)

[Claims] 1. A method of clamping a parison supplied between molds which are close to and separated from each other, blowing air into the clamped parison and blow-molding a hollow molded product, wherein the mold is completely clamped. Until the air is blown from the cavity surface of the mold toward the parison peripheral surface, the parison and the cavity surface are brought into a non-contact state, and when the mold clamping of the mold is completed, the air blow is stopped. A blow molding method for a hollow molded product, characterized in that the parison is deformed following the shape of the cavity surface of the mold by blowing air into the parison. 2. The hollow according to claim 1, wherein the temperature of the air blown from the cavity surface toward the peripheral surface of the parison is lower by 10 ° C. to 30 ° C. than the melting temperature of the resin of the parison. Blow molding method for molded products. 3. The method of blow molding a hollow molded product according to claim 1, wherein said mold is a male and female mold which is close to and separated from each other, and the hollow double wall molded product is blow molded. . 4. When the mold is completely clamped, the blowing of the air is stopped, the air remaining in the gap between the mold cavity surface and the parison is sucked, and the air is blown into the parison. 4. The blow molding method for a hollow molded product according to claim 1, wherein the parison is deformed following the shape of the cavity surface of the mold. 5. A blow molding apparatus for hollow molded articles, wherein the blow molding method for hollow molded articles according to claim 1, 2, 3, or 4 is carried out. 6. The method according to claim 6, further comprising:
A large number of air holes are provided, and an air supply source is connected to these air holes via a switching valve, and air is supplied from the air supply source to the air holes until the mold is completely clamped. 5. The blow molding apparatus according to claim 4, further comprising an air supply control unit configured to switch the switching valve when the mold closing of the mold is completed and to stop supplying the air. 7. The blow molding apparatus according to claim 6, wherein a heater is provided on a secondary side of the air supply source. 8. The blow molding apparatus according to claim 6, wherein said mold is a mold for a hollow double-walled molded product. 9. The heater according to claim 6, wherein said heater is provided for heating the air from said air supply source to a temperature lower by 10 to 30 ° C. than the melting temperature of the parison resin.
Or a blow molding apparatus for hollow molded articles according to 8. 10. A pressure reducing device is connected to said vent hole in parallel with an air supply source via said switching valve, and is provided between a cavity surface of a mold and a parison when supply of said air is stopped. 10. The blow molding apparatus for hollow molded articles according to claim 6, further comprising an air supply / discharge control unit for operating the pressure reducing device to suck air remaining in the gap.